chore: Port FreeSewing.dev to docusaurus

The replaces the NextJS site powering FreeSewing.dev with a Docusaurus
setup. It's part of my efforts to simplify FreeSewing's setup so we can
focus on our core value proposition.

sites/dev/docs/reference/api/utils/splitcurve/readme.mdx

@@ -0,0 +1,80 @@
+---
+title: utils.splitCurve()
+---
+
+The `utils.splitCurve()` function splits a curve defined by 4 points `start`,
+`cp1`, `cp2`, and `end` on the point `split` and returns an array holding both
+halves.
+
+## Signature
+
+```js
+array utils.splitCurve(
+  Point start,
+  Point cp1,
+  Point cp2,
+  Point end,
+  Point check,
+)
+```
+
+## Example
+
+<Example caption="A Utils.splitCurve() example">
+```js
+({ Point, points, Path, paths, utils, part }) => {
+
+  points.start = new Point(10, 10)
+  points.cp1 = new Point(100, 80)
+  points.cp2 = new Point(100, 0)
+  points.end = new Point(10, 50)
+
+  paths.example = new Path()
+    .move(points.start)
+    .curve(points.cp1, points.cp2, points.end)
+    .addClass('dotted stroke-xs')
+
+  points.split = paths.example.shiftFractionAlong(0.4)
+  const halves = utils.splitCurve(
+    points.start,
+    points.cp1,
+    points.cp2,
+    points.end,
+    points.split
+  )
+  for (let i=0; i<2; i++) {
+    const { start, cp1, cp2, end } = halves[i]
+    paths[`segment${i}`] = new Path()
+      .move(start)
+      .curve(cp1, cp2, end)
+      .addClass('stroke-xl')
+      .attr('style', 'stroke-opacity: 0.5;')
+  }
+  paths.segment0.addClass('note')
+  paths.segment1.addClass('lining')
+
+  return part
+}
+```
+</Example>
+
+## Notes
+
+The returned object has this signature:
+
+```js
+[
+  {
+    start: Point,
+    cp1: Point,
+    cp2: Point,
+    end: Point,
+  },
+  {
+    start: Point,
+    cp1: Point,
+    cp2: Point,
+    end: Point,
+  },
+]
+